In the related art, for example, when detaching an insert from a blade surface (blade main unit) of a gas-turbine stator vane disclosed in Patent Literature 1, welding metal that connects an insert collar that protrudes outward from an outer circumferential surface of the insert and a stator-vane-outer-shroud non-gas path surface that surrounds the periphery of the insert collar is worn off with a grinding machine, such as a grinder, etc., and the insert is taken out from a corresponding hollow hole, thus separating the insert from the blade surface.
Note that, from the view points of environment and cost, the blade surface from which the insert is detached and the insert detached from the blade surface are subjected to appropriate refurbishing, etc., as needed, and reassembled to be subsequently reused as a gas-turbine stator vane.